Table 2.

Results of the single studies included in the review.

GnRH agonists
Study	Samples	Methods	Statistical analysis	Endometriosis vs control	Main findings (HT vs NT in endometriosis)		Conclusions
					Endometrium	Vagina
Khan et al. (2014)	Vaginal and endometrial	Bacterial cultures, Gram staining, Nugent scoring system	Chi-square and Kruskal-Wallis tests	↑ sub-clinical uterine infection; ↑ vaginal pH	↑ Gardnerella, Escherichia coli, and Enterococci; ↑ endometritis	↑ intermediate flora (Nugent 4–6); ↓ normal flora (Nugent 0–3); ↑ vaginal pH	GnRHa has a negative impact on vaginal and endometrial microbial communities, favoring the colonization of potentially pathogenic bacteria.
Khan et al. (2016)	Endometrial and cystic fluid	16S rRNA gene sequencing (V3-V4 regions)	Mann–Whitney U-test	In endometrium: ↑ Streptococcaceae and Moraxellaceae; in cystic fluids: ↑ Streptococcaceae, Staphylococcaceae, ↓ Lactobacillaceae	↑ Streptococcacee, Staphylococcaceae and Enterobacteriaceae; ↓ Lactobacillaceae		GnRHa has a negative impact on vaginal and endometrial microbial communities, favoring the colonization of potentially pathogenic bacteria.
Khan et al. (2021)	Endometrial	16S rRNA gene sequencing (V5-V6 regions)	Shannon index, Mann–Whitney U-test	↑ α-diversity	↓ α-diversity; ↑ Gardnerella; ↓ Streptococcus and Prevotella		GnRHa treatment negatively affects microbial diversity, favoring some potentially pathogenic bacteria while impairing others.

Oral contraceptives
Study	Samples	Methods	Statistical analysis	Endometriosis vs control	Main findings (HT vs NT in endometriosis)		Conclusions
					Endometrium	Vagina
Le et al. (2021)	Vaginal	16S rRNA gene sequencing (V4 region)	Faith’s PD index, weithted and unweighted UniFrac metrics, PERMANOVA	Different β-diversity; ↓ α-diversity; ↑ Lactobacillus		Different β-diversity; ↑ α-diversity; ↓ Lactobacillus; ↑ Peptoniphilus, Dialister, Finegoldia, Prevotella and Ureaplasma genera; ↑ Actinobacteria; ↑ B/B ratio	Oral contraceptive pill alters vaginal microbial composition prompting dysbiosis.
Do et al. (2024)	Vaginal	16S rRNA gene sequencing (V4 region)	Faith’s PD index, Bray Curtis metric, Kruskall-Wallis test			↓ α-diversity; Different β-diversity	Hormonal therapy has limited effect within the urogenital tract.
Wee et al. (2018)	Vaginal, cervical and endometrial	16S rRNA gene sequencing (V3 region)	Non-parametric t-test			↑ Streptococcus anginosus, Streptococcus agalactiae, Bifidobacterium breve	Hormonal therapy may favor the colonization of potentially pathogenic bacteria.

B/B ratio, Bacillota/Bacteroidota ratio.